Wozniak Kaitlin T, Elkins Noah, Brooks Daniel R, Savage Daniel E, MacRae Scott, Ellis Jonathan D, Knox Wayne H, Huxlin Krystel R
The Institute of Optics, University of Rochester, Rochester, NY 14627, USA.
Department of Biomedical Engineering, University of Rochester, Rochester, NY 14627, USA.
Exp Eye Res. 2017 Dec;165:20-28. doi: 10.1016/j.exer.2017.08.018. Epub 2017 Aug 31.
Blue-intra-tissue refractive index shaping (Blue-IRIS) is a new approach to laser refractive correction of optical aberrations in the eye, which alters the refractive index of the cornea rather than changing its shape. Before it can be implemented in humans, it is critical to establish whether and to what extent, Blue-IRIS damages the cornea. Here, we contrasted the impact of -1.5 D cylinder refractive corrections inscribed using either Blue-IRIS or femtosecond laser in-situ keratomileusis (femto-LASIK) on corneal cell viability. Blue-IRIS was used to write a -1.5 D cylinder gradient index (GRIN) lens over a 2.5 mm by 2.5 mm area into the mid-stromal region of the cornea in six freshly-enucleated feline eyes. The same correction (-1.5 D cylinder) was inscribed into another four cat eyes using femto-LASIK. Six hours later, all corneas were processed for histology and stained for terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling (TUNEL) and p-γ-H2AX to label damaged cells. In Blue-IRIS-treated corneas, no tissue was removed and TUNEL-stained cells were confined to the laser focal zone in the stroma. In femto-LASIK, photoablation removed 14 μm of anterior stroma, but in addition, TUNEL-positive cells clustered across the femto-flap, the epithelium at the flap edges and the stroma below the ablation zone. Keratocytes positive for p-γ-H2AX were seen adjacent to all Blue-IRIS focal zones, but were completely absent from femto-LASIK-treated corneas. Unlike femto-LASIK, Blue-IRIS attains refractive correction in the cornea without tissue removal and only causes minimal, localized keratocyte death within the laser focal zones. In addition, Blue-IRIS induced DNA modifications associated with phosphorylation of γ-H2AX in keratocytes adjacent to the laser focal zones. We posit that this p-γ-H2AX response is related to alterations in chromatin structure caused by localized changes in osmolarity, a possible mechanism for the induced refractive index changes.
蓝色组织内折射率塑形（Blue-IRIS）是一种用于眼部光学像差激光屈光矫正的新方法，它改变角膜的折射率而非其形状。在将其应用于人类之前，确定Blue-IRIS是否以及在何种程度上会损伤角膜至关重要。在此，我们对比了使用Blue-IRIS或飞秒激光原位角膜磨镶术（飞秒LASIK）进行-1.5 D柱镜屈光矫正对角膜细胞活力的影响。在六只新鲜摘除的猫眼中，使用Blue-IRIS在角膜基质中部2.5毫米×2.5毫米的区域内写入一个-1.5 D柱镜渐变折射率（GRIN）透镜。使用飞秒LASIK在另外四只猫眼中进行相同的矫正（-1.5 D柱镜）。六小时后，对所有角膜进行组织学处理，并进行末端脱氧核苷酸转移酶介导的dUTP-地高辛配基缺口末端标记（TUNEL）和p-γ-H2AX染色，以标记受损细胞。在接受Blue-IRIS治疗的角膜中，没有组织被去除，TUNEL染色的细胞局限于基质中的激光聚焦区。在飞秒LASIK中，光消融去除了14微米的前基质，但此外，TUNEL阳性细胞聚集在飞秒瓣、瓣边缘的上皮以及消融区下方的基质中。在所有Blue-IRIS聚焦区附近均可见p-γ-H2AX阳性的角膜细胞，但在接受飞秒LASIK治疗的角膜中则完全没有。与飞秒LASIK不同，Blue-IRIS在不切除组织的情况下实现角膜屈光矫正，并且仅在激光聚焦区内引起最小程度的局部角膜细胞死亡。此外，Blue-IRIS在激光聚焦区附近的角膜细胞中诱导了与γ-H2AX磷酸化相关的DNA修饰。我们推测这种p-γ-H2AX反应与渗透压局部变化引起的染色质结构改变有关，这可能是诱导折射率变化的一种机制。
